A personal watercraft is a new recreational vehicle which has had a resounding commercial success during the last several years. However, personal watercraft suffer from complaints of noise pollution.
Several countries, such as the United States and France are studying the possibility of passing regulations which will limit the noise of a personal watercraft to 80 DB(A) at a distance of 7.5 m. Prior art personal watercrafts usually emit more than this level. Thus, there is a need in the industry to provide a personal watercraft which emits a more tolerable level of DB(A).
Studies have showed that personal watercraft noise problems are complex because the noise comes from multiple sources and follow multiple transfer paths. Indeed, sources may be divided into three categories (i) structural noise which is related to the hull radiating noise coming from induced efforts created by the jet pump and other mechanical elements fixed to the structure (mechanical excitation); (ii) aerial noise which corresponds to the noise emitted by acoustical wave transmission produced by the muffler walls and the air intake (acoustical excitation); and (iii) direct noise such as muffler outlet or jet pump flow.
It has been shown that insulating the pump from the hull will reduce the noise coming from the pump itself and from the motor via the shaft (mechanical excitation). If has also been shown that it is possible to reduce the acoustical excitation by insulating some noise generating components.
An object of the present invention is to provide a noise reducing system which reduces the noise generated by a personal watercraft.
A further object of the invention is to provide a pump insulating system which reduces structural noise coming from the pump, and from the motor via the shaft, without substantially decreasing the performance of the pump.
As embodied and broadly described herein, the invention seeks to provide a pump insulating system for a personal watercraft having a pump housing and a rear supporting wall, said insulating system including at least one insulating attachment for connecting said pump housing to said rear supporting wall, said insulating attachment including at least one T-shaped insulator having a longitudinal aperture and a portion mounted between said pump housing and said rear supporting wall, a sleeve within the longitudinal aperture of said insulator, and a threaded rod extending through said sleeve for retaining said pump housing to said rear supporting wall.
The invention further seeks to provide a personal watercraft including a hull having an internal duct leading from a water inlet portion to a rearward outlet and a rear supporting wall, an engine mounted in said hull, a shaft extending rearwardly from the engine toward an impeller, said impeller is rotatably journaled in a pump housing, said pump housing is attached to said rear supporting wall, wherein the improvement includes a pump insulating system comprising at least one insulating attachment for connecting said pump housing to said rear supporting wall, said insulating attachment including an insulator having a portion mounted between said pump housing and said rear supporting wall.
In a preferred embodiment of the present invention the novel noise reducing system for use on a personal watercraft comprises: an air intake tube having an insulating foam inside; a pump insulating system having at least one insulating attachment; said insulating attachment comprising a threaded rod, a sleeve having an aperture in which the threaded rod is inserted and at least one T-shaped rubber insulator; a muffler including a shield mounted thereon; the shield having a first polyurethane foam layer and a second composite layer; and a resonator made of moulded plastic mounted on an exhaust pipe.
Other objects and features of the invention will become apparent by reference to the following specification and to the drawings.